 (defn typical-stage-top []
   (tuc/draw-normal 13750 2150))
 
-(defn typical-stage-length []
-  (tuc/draw-normal 152 17))
+(defn typical-stage-length
+  ([] (let [length-unit (rand-nth [:ft :m])]
+        [length-unit (typical-stage-length length-unit)]))
+  ([length-unit]
+   (condp = length-unit
+     :ft [:ft (tuc/draw-normal 152 17)]
+     :m [:m ((convert-units-f :ft :m) (nth (typical-stage-length :ft)))])))
 
 (defn typical-stage-extent
   ([]

  #?(:cljs (:require [test-utils.core :as tuc])
     :clj (:require (test-utils [core :as tuc]))))

(defn typical-vertical-depth []
  (tuc/draw-normal 8000 1216))


        sigma (/ mean 6)]
    (tuc/draw-normal mean sigma)))

(def physical-quantities [:length :mass :pressure :volume :injection-rate :proppant-concentration])

(defn rand-physical-quantity []
